Under the 3GPP standards, a NodeB (or an eNB in LTE) is the base station via which mobile devices connect to the core network. Recently the 3GPP standards body has adopted an official architecture and started work on a new standard for home base stations (HNB). Where the home base station is operating in accordance with the (Long Term Evolution) LTE standards, the HNB is sometimes referred to as a HeNB. A similar architecture will also be applied in the WiMAX network. In this case, the home base station is commonly referred to as a femto cell. For simplicity, the present application will use the term HNB to refer to any such home base station and will use the term base station generically to refer to other base stations (such as the base station for the macro cell in which a HNB operates). One or more HNBs will provide radio coverage (for example, 3G/4G/WiMAX) within the home and will connect to the core network via one or more suitable public networks (for example via an ADSL link to the Internet) and in the case of the 3GPP standards, via an HNB gateway (HNB-GW) which will aggregate traffic from the one or more HNBs.
The current specification for the 3GPP standards require the Information Element (IE) “Unsuccessfully Transmitted DL Data Volume” to be reported when a call is finally released as the charging policy may depend on the successful packet count. The serving base station keeps a count of the unsuccessful DL data packets so that this can be reported when the call is released. However, as the User Equipment (UE), such as a mobile telephone, moves around with the user, it is likely that during the call, the UE will roam between cells. When roaming between macro cells, the Iu connection between the source base station and the core network will be released and a new Iu connection established by with the target base station. The core network can therefore aggregate the unsuccessful packet counts for each of the base stations involved in the call. However, the inventor has realised that when a UE moves from one HNB to another HNB, the Iu connection between the HNB-GW and the Core Network will not be released during the handover and so the core network will not be able to keep track of the unsuccessful packet count.
The present invention has been made to address this problem. The inventor has realised that this problem can be addressed by making the HNB-GW or at the HNB(s) involved in the handover responsible for aggregating the unsuccessful DL data packets, so that when the call is finally released, the total aggregated count of unsuccessful DL packets is reported to the core network.